Electrodeposition of cuprous oxides and baths therefor



March 9 1943. J. E. ST ARECK 2,313,454 ELECTRODEPQSITIQN 0F CUPROUS OXIDE AND BATH THEREFOR Filed May 24, 1938 curren ffcle hsi cy s inqle lecirode voliagg atented Mar. 9, 1943 OFFICE 2,313,454 ELEC'KRQGSITION F CUPROUS OXIDES Jesse E. Stareck, Wat

BATHS THEREFOR erbury, Conn, assignor to Kansas City Testing Laboratory,

Kansas City,

Mo., a corporation of Missouri Application May 24, 1938, Serial No. 209,835

12 Claims.

. an additional or extra voltage required which I designate as the extra single-electrode voltage. After the initial stage of deposition, the voltage usually falls. These conditions are causes of uncertainty and irregularity in operation, particularly when employed for the production of decorative coatings or color-efiects.

I have discovered that by providing in the bath a micelles or nuclei of the cuprous oxide to be deposited (an anhydrous or a hydrated oxide), the operation is made certain and regular. With such micelles or nuclei present in the plating bath the extra single electrode voltage at the start, heretofore referred to, is almost entirely eliminated, and very little additional energy, or extra voltage, is necessary to start the electrodeposition of the non-metallic coating on metal surfaces.

By the present invention a process and baths for use therein are provided in which optimum performance is obtained, and in which the isorhelc range of single-electrode-voltageg is wide, constant and regular. The initial single=electrade-voltage, that is the metal to non-metal over-voltage, or the voltage at which cuprous oxide is first electrodeposited on the electrode, is decreased in some instances from about 0.1 volt, for freshly prepared baths, to practically zero, for baths embodying the present improvements and possessing isorhelc ranges beginning approximately 0.1 volt lower than otherwise. The micelles provided according to this invention are compounds of copper, comprising cuprous oxide, which appear to act as nuclei for the formation of cuprous oxide, and by means of which the electrodeposition of cuprous oxide can easily start.

A wide isorhelc range, especially with an initial single-electrode-voltage which is low with respect to the initial voltage for a process and bath not embodyingthe present improvements, is characterizm by good throwing power and covering ability.

ing to the present invention compared with the character of the process and baths which do not embody the present improvements is illustrated graphically by the two curves a and b on the accompanying graph of cathodesingle-electr0devoltages and current-densities. The curve a represents the relationship between single-electrodevoltages and current densities for the process when carried out in baths provided with micelles according to the present invention, and b represents a similar curve for the process when carried out in baths without the improvements described herein. A comparison of the two curves shows the curve a has a much more regular progression from zero to the point at which its isorhelc range begins than has the 'curve b.

I have discoveredthat the micelles or nuclei may be provided in the bath in a number of ways. For example, substances may be added which yield the micelles or nuclei; substances may be added which react with the ingredients of the bath to yield the micelles or nuclei; and substances may be added which in conjunction with energy. such as that derived from heat, light, or electricity, act on the ingredients of the bath in such a way as to yield the micelles or nuclei.

As heretofore indicated, one mode of providin the micelles in the baths is to add certain sparingly soluble, very finely divided copper comin small quantities) which yield pounds (usually the micelles. Examples of such substances are copper oxides (anhydrous and/or hydrated) The character of the process and baths accordwherein the copper constituent has the same valence as its valence in cuprous oxide which is electrodeposited on the article to form the coating.

Example I Two g./l. of moist finely divided cuprous oxide were added to an alkalin cuprilactate bath having the following make-up composition.

Copper lactate g./l- Sodium lactate (50%) cc./l 200 Caustic soda -g./l 30 of the plating Another mode of providing micelles in the bath is to add substances which react with the ingredients of the bath to yield the micelles or nuclei. Such substances may be oxidizing agents or reducing agents. The oxidizing agents are understood to react with the organic radicals of the plating bath to form active intermediate oxidation products, which intermediate oxidation products further react with the copper constituent bath in such a way as to cause partial chemical reduction of the copper constituent. The reducing agents are understood to react chemically directly with the copper constituent of the plating bath tocause partial chemical reduction of the copper constituent.

Examples of substances acting as oxidizing agents are dissolved oxygen, dissolved air, hydrogen peroxide, alkali metal peroxides, hypochlorites, etc. In general substances which are chemically active as oxidizing agents can be used.

Example II Air was bubbled through 180 gallons of a bath having the composition given in Example I, for four hours. Marked improvement in throwing power and. general plating performance of the bath was obtained. When air was bubbled for longer periods of time a slight additional improvement was noted, but no further effect was perceptible beyond a short period after the four hours.

Examples of substances acting as reducing agents are those which contain a carboxy grouping of the aldehyde or of the ketone type such as soluble pyruvates or pyruvic acid, aldol, dextrose, crotonaldehyde, acetaldehyde, or, reducing agents not containing an active aldehyde or ketone carboxy grouping, such as cane-sugar, hydroxylamine or hydrazine. I generally prefer, however to use reducing agents containing an aldehyde or ketone carboxy grouping.

Example III Two grams of aldol was added to a bath having the composition given in Example I. After about three hours, excellent deposits with uniform throwing power were obtained. The improvement was maximum in about five hours.

In the case of substances which act as oxidizing or reducing agents I generally prefer to use from one-eighth to five g./l. of the substances.

Another mode of providing the micelles in the bath is to add substances which are electrolytes, which are neither oxidizinglpr reducing agents in themselves, but which increase the sensitivity of the metallo-organic complexes of the plating bath to the action of energy such as light, electricity, or heat, and which, as a result insure a potential supply of readily available micelles or nuclei of partially reduced copper compounds.

Examples of substances which increase the sensitivity of the metallo-organic complexes to the action of energy are alkali metal carbonates, acetates, phosphates, sulphates. etc. Most of the substances in this group are buffer agents which, beside acting to yield micelles or nuclei under the action of energy, tend to stabilize the hydrogen ion concentration (pl-I) of the plating bath. It is usually advantageous to use from 20 to 50 g./l. of these substances.

Example IV 20 to 50 g./l. of sodium carbonate (NazCOa) was added to a bath having the composition given in Example I. Some initial improvement the micelles or nuclei in conjunction with energy,

with a substance or substances of the other types.

In carrying out the process, a bath suitable for electrodepositing cuprous oxide (such as the bath of the composition given under Example I, or any of the baths mentioned in my Patent #2,081,121) is made up, and treated to provide micelles or nuclei or the cuprous oxide to be electrodeposited. After the requisite time for the formation of the micelles or nuclei,,articles to be coated with a cuprous-oxide electrodeposit, are suspended in thesolution connected to the proper terminal or bus (cathode) of an electric circuit,

and an electric current passed through the solution.

When air is used for stirring, oragitating the bath solution during the course of the electrolytic deposition, the addition initially of one or more of the substances for providing the micelles is generally all that is required, inasmuch as the air used for agitation provides for the maintenance of an adequate amount of dissolved air (oxygen) in the bath solution. When mechanical agitating means are used, small additions of one or more of the hereinbefore described substances for providing the micelles are made from time to time. Additions of the substance for adding or providing the micelles are occasionally made even when air is used for agitation, as when low bath temperatures are used, and when there has been a considerable depletion of the bath constituents or a rather large addition of the make-up ingredients made to the solution. Operating conditions are advantageously practiced in accordance with my Patent #2,081,121.

Other formsof baths, other modes of adding or providing micelles or nuclei in the baths, and other modes of carrying out the process, than those herein specifically described may be used or practiced.

What is claimed is:

1. In a process of electrodepositing cuprous oxide from baths containing in solution copper compounds in which the copper is in the cupric state, and cupric ions, adding to the said bath a substance for eifecting an increase of miscelles or nuclei containing cuprous oxide, by which the initial single-electrode voltage at which cuprous oxide is electrodeposited is lowered, and with the bath so conditioned, passing an electric current through said bath from an anode to an article-cathode therein.

2. A bath for electrodepositing cuprous oxide containing in alkaline solution copper compounds in the form of complexes in which the copper is in the cupric state, and cupric ions, characterized by the bath containing micelles or nuclei, comprising cuprous oxide and to which has been added a substance for effecting an increase of e the micelle content, the micelles being coni .tained, in quantities over and above the amount produced spontaneously and by the flow of current used in the operation of the bath without the addition.

3. In a method of electrodepositing cuprous oxide coatings from baths containing cupric copper organic radical complexes, the step of improving the throwing power and covering ability which comprises adding to the bath an oxidizing agent which oxidizes constituents of the bath to .in turn partially reduce the copper constituent in the bath to form micelles or nuclei comprising cuprous oxide, in quantities over and above the amount produced spontaneously and by the flow of current used in the operation of the bath without the addition.

4. In a method of electrodepositing cuprous oxide coatings from baths containing cupric copper organic radical complexes, the step of improving the throwing power and covering ability which comprises adding to the bath an organic compound different from that of the organic portion of the copper organic radical complex, said compound acting as a reducing agent to partially reduce the copper constituent in the bath to form micelles or nuclei comprising cuprous oxide, in quantities over and above the amount produced spontaneously and by the flow of current used in the operation of the bath without the addition.

5. In a method of electrodepositing cuprous oxide coatings from baths containing cupric copper radical complexes the step of improving the. throwing power and covering ability which comprises adding to the bath micelles or nuclei comprising cuprous oxide, over and above the amount produced spontaneously and by the flow of current used in the operation of the bath without the addition.

6. In a method of electrodepositing cuprous oxide coatings from baths containing cupric copper radical complexes, the step of improving the throwing power and covering ability according to claim 1, further characterized by the micelles being added from time to time to maintain the efiiciency of the bath in throwing power and covering ability.

7. In a method of electrodepositing cuprous oxide coatings from baths containing cupric copper organic radical complexes, the step of improving the throwing power and covering ability which comprises adding to the bath reducing agents containing carboxy groups of the aldehyde or of the ketone type.

8. In a method of electrodepositing cuprous oxide coatings from baths containing cupric cop: per organic radical complexes, the step of improving the throwing power and covering ability according to claim 7, of the addition are from one-eighth to five grams per liter of the bath.

9. A bath for electrodepositing cuprous oxide according to claim 2, wherein the micelles are provided by the addition of a compound containing the micelle. I i

10. A bath for electrodepositing cuprous oxide according to claim 2, wherein the micelles are provided by the addition of a substance which reacts with copper compounds in the bath to form the micelle.

11. A bath for electrodepositing cuprous oxide according to claim 2; wherein the micelles are provided by the addition of a substance which reduces copper compounds in the bath to form the micelle.

12. A bath for electrodepositing cuprous oxide according to claim 2, wherein the micelles are provided by the addition of a substance which oxidizes constituents of'the bath to in turn reduce copper compounds in the bath to form the micelle.

' JESSE E. $TARECK.

wherein the quantities 

